I have 150mm of insulation in the floor (over beam and block). I've used sheets of 50mm and 100mm, only because i bought a load of 100mm seconds. Question is - can i get the plumbers to put my hot water pipes OVER the 50mm and UNDER the 100mm, rather than have the pipes underneath it all, sitting directly on the dpm/concrete, which is what they are planning to do.

It seems daft that my lovely hot (pv heated) water would run from the tank, then go underneath all the house insulation, run on 8 meters of exterior temperature cold concrete, before coming back up into the warm house, to the shower, ...when it could sit on 50mm of insulation…?
We did a beautiful job with the insulation (we could overlap the joins etc), so i imagine there won't be much heat escaping down to prevent freezing pipes either.

Would having it within the insulation be legal, or sensible? Building regs or any other restriction?
We have used Celotex and Retocel insulation boards.

When I wanted a similar thing from my plumber, who was about to put the pipes onto the slab with all the insulation going on top (100+100 layers cross layed), as he wanted to be able to fix the main supply pipe to the ground securely (not just to 100mm PIR sheeting). The solution was that strips of insulation were put under the pipes, but such that they could still be well anchored to the concrete with straps/brackets. Then rest of the insulation fitted around it. A bit of a jigsaw, but the chippie laying the PIR made light work of it. Plummer had laid the pipe nice and linearly which made it easier.

Could you poor/spray a PVA solution onto it, or at least make a sample up and see if it works.

Seems that I posted in the wrong thread, I thought this one was about the whacking of floor and the foamglass.

Also, now I remember, the plumber and builder didn't want the first PIR layer down all over at the time the pipes were going in. They said they would ruin it while tramping over it dragging kit etc. while working, actually they thought I was bonkers to suggest it. I am glad I listened, it would have been wrecked. But they also understood that insulation below pipes was a good idea, and that I wanted more than the 10mm pipe stuff they normaly fitted. They fitted that too as "belt and braces".

There was a big cleanup before the PIR sheets finally went down, and the UFH pipes and anhydrite screed went down immediately afterwards taking care to minimise possible damage to the PIR.

No, standard building practices are just not thought through from an insulation perspective. Liase with your tradesmen well in advance over what you want to achieve, so it can be worked into the build and everyone happy.

Like treeplanter I am planning to run hot and cold water pipes (not UFH pipes) in between layers of floor insulation, yes a PITA logistically but doable if planned right. As long as you have no joins to tees it should not be a problem.

Are they "heating pipes or hot water pipes if hot water pipes insulated and as short as possible

Op said " heating pipes" where is it that they need to distribute the heat ?

Posted By: bxmanHave I missed something ?

What are you trying to heat ?

It's DHW pipes, not UFH. I was confused at first too

Posted By: treeplanterts kneeling on it that really seems to wreak it!

plus the doorway bits !

gg